Olefin metathesis method using a catalyst containing aluminum and molybdenum

ABSTRACT

The invention relates to a process for the metathesis of olefins implemented with a catalyst comprising a mesoporous matrix and at least the elements molybdenum and aluminum, said elements being incorporated into said matrix by means of at least one precursor comprising molybdenum and aluminum.

The present invention relates to a process for the metathesis of olefinsusing a catalyst prepared from a heteropolyanion salt comprisingmolybdenum and aluminium.

PRIOR ART

The metathesis of olefins is an important reaction in various fields ofchemistry. In organic synthesis, this reaction, catalyzed byorganometallic complexes, is used in order to obtain various high addedvalue molecules. In petrochemistry, the metathesis of olefins is ofgreat practical interest in particular for the rebalancing of lightolefins originating from steam cracking, such as ethylene, propylene andbutenes. In particular, the cross metathesis of ethylene with 2-butenein order to produce propylene is a reaction of interest given theincreasing use of propylene in the market.

Different types of catalysts are capable of being used in the metathesisreaction. It is possible to use homogeneous catalysts, the constituentelements of which are all soluble in the reaction medium, orheterogeneous catalysts which are insoluble in the reaction medium.

The metathesis of light olefins utilizes heterogeneous catalysts. Aknown solution is the technology described in U.S. Pat. No. 8,586,813,which uses a catalyst based on tungsten oxide deposited on a silicasupport WO₃/SiO₂. However, the heterogeneous catalysts based on tungstenoperate at a relatively high temperature, generally at a temperaturegreater than 300° C. and are only moderately active.

Moreover, it is known that metathesis catalysts based on rhenium oxideRe₂O₇ such as those described in the publication by Chauvin et al.Journal of Molecular Catalysis 1991, 65, 39 have good activities attemperatures close to ambient temperature. Other catalysts based onmolybdenum oxide such as those described in the publication D. P.Debecker et al., J. Catal., 2011, 277, 2, 154 and patents GB 1,164,687and GB 1,117,968 owned by the company Shell have been also developed.Shell's process uses, for example, catalysts based on molybdenum andcobalt oxides deposited on an aluminium support CoMoO₄/Al₂O₃ and dopedwith phosphorus, as described in U.S. Pat. No. 4,754,099.

One benefit of molybdenum (Mo) is that it is less expensive than rhenium(Re). In addition, its stability and its activity are intermediatebetween those of rhenium (Re) and tungsten (W). In particular,molybdenum can be active starting from ambient temperature.

The preparation of catalysts based on molybdenum oxides (MoO₃) iscarried out in a standard fashion by impregnation with an aqueoussolution of a molybdenum salt or a heteropolyanion containing molybdenumsuch as for example the isopolyanion ammonium heptamolybdate on asupport such as silica, alumina or a porous aluminosilicate. Thecatalysts prepared from precursors of the ammonium heptamolybdate typehowever lack activity and stability. Catalysts based on otherheteropolyanions, such as H₃PMo₁₂O₄₀ have been prepared and make itpossible to appreciably increase activity, but need further improvement.

Therefore there is still a need to develop new catalysts having improvedperformances in terms of activity and selectivity for the metathesisreaction of olefins and more particularly for the metathesis betweenethylene and 2-butene for the production of propylene.

The Applicant, in his research to improve the performances of theheterogeneous catalysts for the metathesis of olefins, has developed newcatalysts for the metathesis reaction of olefins. These catalysts areprepared from a mesoporous matrix and at least one heteropolyanion saltcomprising molybdenum and aluminium. Unexpectedly, it has been foundthat the use of these types of precursors for the preparation of thecatalyst according to the invention improved the activity and thestability of the heterogeneous catalyst obtained for the metathesisreaction of olefins, compared with the catalysts prepared using otherprecursors of the prior art. The conversion of the olefins is therebyimproved. The stability of the catalyst is also improved.

An objective of the present invention is to provide a process for themetathesis of olefins using a catalyst having improved performances interms of activity and selectivity compared with the use of heterogeneouscatalysts of the prior art.

The catalysts according to the invention have the advantage of beingable to operate over longer time cycles before regeneration, which has asignificant economic impact on the operating costs of the processaccording to the invention.

SUBJECT OF THE INVENTION

The present invention relates to a process for the metathesis of olefinscarried out by bringing the olefins into contact with a catalystcomprising a mesoporous matrix and at least the elements molybdenum andaluminium, said elements being incorporated into said matrix by means ofat least one precursor comprising molybdenum and aluminium.

Advantageously, the precursor according to the present invention is aprecursor of heteropolyanion salt type based on molybdenumadvantageously corresponding to formula (I)(Al_(a)Mo_(m)M_(b)X′_(x)O_(y)H_(h))^(q−)(C^(r+))_(c) .nH₂O  (I)in which,

-   -   a is greater than or equal to 0, preferably less than or equal        to 1,    -   m is greater than or equal to 1, preferably less than or equal        to 18,    -   b is greater than or equal to 0, preferably less than or equal        to 18,    -   x is greater than or equal to 0, preferably less than or equal        to 2,    -   y is greater than or equal to 10, preferably less than or equal        to 70,    -   h is comprised between 0 and 12,    -   q is comprised between 1 and 20,    -   r is comprised between 1 and 20,    -   c is comprised between 1 and 20,    -   n is comprised between 0 and 200,    -   x, m, y, h, n and q being integers, M being a metallic element        other than aluminium and molybdenum selected from zinc, nickel,        cobalt, tungsten, vanadium, niobium, tantalum, iron and copper,        preferably M is cobalt, tungsten and vanadium, and X′ being an        element selected from phosphorus, silicon and boron, preferably        X′ is phosphorus,    -   C represents one or more atoms, identical or different, hydrated        or non-hydrated, selected from the elements of the periodic        table are capable of existing in the cationic form, such as        hydrogen, the alkali, alkaline-earth elements, transition        metals, post-transition metals and rare earths, in hydrated or        non-hydrated forms, selected from the oxygen-containing and/or        nitrogen-containing and/or phosphorus-containing organic        cations, such as the ammonium and phosphonium cations.

According to the invention, the precursor of the heteropolyanion salttype according to the invention can be stabilized by one or moreadditional organic species selected from oxygen-containing and/ornitrogen-containing organic molecules, such as histidine, piperazine,choline, urea, the copper complexes of phenantroline, acetate ion,acetic acid, used alone or in a mixture.

One or more precursors of the heteropolyanion salt type corresponding toformula (I) can be used.

The precursor of the heteropolyanion salt type according to theinvention can contain one or more metallic elements M selected fromzinc, nickel, cobalt, tungsten, vanadium, niobium, tantalum, iron andcopper, in substitution for one or more molybdenum atoms contained insaid precursor. Preferably, the metallic element M is selected fromcobalt, tungsten, vanadium.

When the precursor of heteropolyanion salt type used in the preparationof the catalyst utilized in the metathesis process according to theinvention does not contain a metallic element M and does not contain anelement X′, it is advantageously selected from the group formed by theAnderson heteropolyanion salts of formula AlMo₆O₂₄H₆ ³⁻(C^(r+))_(c).nH₂Othat can also be found written as the formula Al(OH)₆Mo₆O₁₈³⁻(C^(r+))_(c).nH₂O, C and c corresponding to the definition accordingto the invention. For example, the precursor of the Andersonheteropolyanion salt type can be selected from[Al(OH)₆Mo₆O₁₈]³⁻[(C₆H₁₀N₃O₂)₂Na(H₂O)₂]³⁺6H₂O(C₆H₁₀N₃O₂=histidinium);[Al(OH)₆Mo₆O₁₈]³⁻ ₂{Na₂[Me₃N(CH₂)₂OH]₄}⁶⁺.8NH₂CONH₂.4H₂O;[Al(OH)₆Mo₆O₁₈]³⁻.(H₃O⁺)[Cu(C₆NO₂H₄)(phenantroline)(H₂O)]⁺ ₂.5H₂O;[Al(OH)₆Mo₆O₁₈]³⁻[Al(H₂O)₆]³⁺.10H₂O, [Al(OH)₆Mo₆O₁₈]³⁻[(NH₄)]₃.7H₂O.

When the precursor of the heteropolyanion salt type according to theinvention used in the preparation of the catalyst utilized in themetathesis process according to the invention contains a metallicelement M other than molybdenum and aluminium, M is preferably tungstenor vanadium, and/or contains another element X′, X′ is preferablyphosphorus, it is advantageously selected from the group formed by theAnderson heteropolyanion salts of formula [AlWMo₈O₃₂]⁷⁻[Na]₇.11H₂O;[AlWMo₈O₃₂]⁷⁻[K]₇.14H₂O and the Keggin heteropolyanion salts of formula[PMo₁₁Al_(0.5)V_(0.5)O₄₀]⁵⁻[H⁺]₅; [PW₉Mo₂AlO₄₀H₂]⁴⁻[NBu₄ ⁺]₄.

The mesoporous matrix according to the invention is advantageously amatrix based on the oxide of at least one element X selected fromsilicon, aluminium, titanium, zirconium, magnesium, lanthanum, ceriumand mixtures thereof. Preferably, the mesoporous matrix according to theinvention is advantageously a matrix based on the oxide of at least oneelement X selected from silicon, titanium, zirconium, magnesium,lanthanum, cerium and mixtures thereof. Preferably, the element X issilicon or a mixture of aluminium and silicon. More preferably, theelement X is silicon.

Said matrix based on oxide described as mesoporous is understood to meanaccording to the present invention a matrix comprising pores the size ofwhich varies between 2 and 50 nm according to the IUPAC classification(K. S. W. Sing, D. H. Everett, W. R. A. Haul, L. Moscou, J. Pierotti, J.Rouquerol, T. Siemieniewska, Pure Appl. Chem. 1985, 57, 603), and/or amesostructured mesoporous matrix, i.e. having mesopores of uniform sizeand distributed periodically through said matrix and/or a matrix withhierarchical porosity, i.e. comprising micropores and/or macropores inaddition to the mesopores.

Preferentially, a mesoporous matrix is used based on silicon oxidehaving a specific surface area of 50 to 1200 m²/g, and preferably from150 m²/g to 1200 m²/g, and a pore volume of at least 0.1 ml/g, andpreferably a pore volume comprised between 0.2 and 1.2 ml/g according tothe BET method.

The catalyst used according to the invention comprises a content byweight of molybdenum element provided by the precursor of formula (I)according to the invention comprised between 1 and 40%, preferablybetween 2 and 30%, preferably between 2 and 20%, expressed as apercentage by weight of molybdenum with respect to the weight of themesoporous matrix.

The catalyst used according to the invention comprises a content byweight of aluminium element provided by the precursor of formula (I)according to the invention comprised between 0.01 and 50%, preferablybetween 0.02 and 35%, preferably between 0.02 and 25% expressed as apercentage by weight of aluminium element with respect to the weight ofthe mesoporous matrix.

The catalyst according to the invention can be prepared according to themethods known to a person skilled in the art.

In a variant of the process for the preparation of the catalyst usedaccording to the invention, the precursor comprising molybdenum andaluminium is deposited on the surface of a preformed mesoporous matrixbased on oxide.

The preformed mesoporous matrix can be commercial or synthesizedaccording to the methods known to a person skilled in the art, inparticular by use of the “traditional” inorganic synthesis methods:precipitation/gelation from salts under mild temperature and pressureconditions; or “modern” metallo-organic: precipitation/gelation fromalkoxides under mild temperature and pressure conditions. In theremainder of the text and for the sake of clarity, these methods aresimply called “sol-gel”.

The preformed mesoporous matrix can be in the form of powder or formed,for example in the form of pelletized, crushed or sieved powder,granules, tablets, beads, wheels, spheres or extrudates (cylinders whichcan be hollow or not, multilobed cylinders with 2, 3, 4 or 5 lobes forexample, twisted cylinders), or rings, etc.

The deposition or incorporation of the precursor according to theinvention on the mesoporous matrix can be done before, during or afterthe forming of the mesoporous matrix.

The deposition or incorporation of the precursors according to theinvention on the mesoporous matrix can be carried out by methods calleddry impregnation, impregnation in excess, CVD (chemical vapourdeposition), CLD (chemical liquid deposition), etc. described forexample in “Catalysis by transition metal sulphides, from moleculartheory to industrial application, Eds Hervé Toulhouat and PascalRaybaud, p 137”.

The catalyst can be prepared by dry impregnation according to theprocess comprising the following stages:

a) solubilization of the precursor comprising molybdenum and aluminium,of formula (I) in a volume of solution corresponding to the pore volumeof a preformed mesoporous matrix based on oxide,

b) impregnation of the preformed mesoporous matrix based on oxide withthe solution obtained in stage a), optional maturation of the solid thusobtained,

c) optional stage of drying, calcination and/or steam treatment of thesolid obtained at the end of stage b), at a pressure greater than orequal to 0.1 MPa or less than or equal to 0.1 MPa, in a temperaturerange from 50° C. to 1000° C.,

d) stage of thermal activation of the solid obtained at the end of stagec), at a pressure greater than or equal to 0.1 MPa or less than or equalto 0.1 MPa, in a temperature range from 100° C. to 1000° C.

The maturation optionally implemented in stage b) is carried out in acontrolled atmosphere and at a controlled temperature so as to promotethe dispersion of said precursor over the entire surface of thepreformed mesoporous matrix based on oxide. Advantageously, thematuration is carried out at a temperature comprised between 20 and 120°C. and a pressure comprised between 0.01 and 1 MPa.

Stages c) and/or d) can be carried out under an oxidizing, reducing orneutral atmosphere.

Preferably, optional drying stage c) is carried out in a temperaturerange from 20° C. to 200° C., preferably from 50° C. to 150° C. andpreferably from 100° C. to 130° C. during a period of less than 72 h andpreferably less than 24 h.

Preferably, thermal activation stage d) is carried out under a neutralatmosphere at atmospheric pressure in a temperature range from 200° C.to 800° C., preferably from 350° C. to 650° C. Preferably, the neutralatmosphere is nitrogen in a flow rate range from 0.01 to 20 NI/h pergram of solid obtained at the end of stage c), preferably from 0.1 to 10NI/h per gram of solid obtained at the end of stage c).

The catalyst can be prepared by impregnation in excess, according to theprocess comprising the following stages:

a′) solubilization of the precursor comprising molybdenum and aluminiumof formula (I), in a volume of solution corresponding to between 1.5 and20 times the pore volume of the preformed mesoporous matrix based onoxide,

b′) impregnation of the preformed mesoporous matrix based on oxide, withthe solution obtained in stage a′), filtration and recovery of thesolid, optional maturation of the solid thus obtained,

c′) optional stage of drying, calcination and/or steam treatment of thesolid obtained at the end of stage b′) at a pressure greater than orequal to 0.1 MPa or less than or equal to 0.1 MPa, in a temperaturerange from 50° C. to 1000° C.,

d′) stage of thermal activation of the solid obtained at the end ofstage c′) at a pressure greater than or equal to 0.1 MPa or less than orequal to 0.1 MPa, in a temperature range from 100° C. to 1000° C.

The maturation optionally implemented in stage b′) is carried out in acontrolled atmosphere and at a controlled temperature so as to promotethe dispersion of said precursor over the entire surface of thepreformed mesoporous matrix based on oxide. Advantageously, thematuration is carried out at a temperature comprised between 20 and 120°C. and a pressure comprised between 0.01 and 1 MPa.

Preferably, the solubilization of the precursor comprising molybdenumand aluminium of formula (I) in stage a) is carried out in a volume ofsolution corresponding to between 2 and 10 times the pore volume of thepreformed mesoporous matrix based on oxide.

Stages c′) and/or d′) can be carried out under an oxidizing, reducing orneutral atmosphere.

Preferably, optional drying stage c′) is carried out in a temperaturerange from 20° C. to 200° C., preferably from 50° C. to 150° C. andpreferably from 100° C. to 130° C. during a period of less than 72 h andpreferably less than 24 h.

Preferably, thermal activation stage d′) is carried out under a neutralatmosphere at atmospheric pressure in a temperature range from 200° C.to 800° C., preferably from 350° C. to 650° C. Preferably, the neutralatmosphere is nitrogen in a flow rate range from 0.01 to 10 NI/h pergram of solid obtained at the end of stage c′), preferably from 0.1 to 5NI/h per gram of solid obtained at the end of stage c′).

Organic compounds, called organic additives, can also be used during thepreparation of the catalyst according to the invention. At least oneorganic additive can be introduced by impregnation onto the mesoporousmatrix before the stage of impregnation with the precursor (stage b orb′), by co-impregnation with the precursor or post-impregnation afterimpregnation with the precursor.

The organic compounds or additives used are selected from chelatingagents, non-chelating agents, reducing agents and additives known to aperson skilled in the art.

Said organic compounds or additives are advantageously selected frommono-, di- or polyalcohols optionally etherified, carboxylic acids(citric acid, acetic acid, etc.), sugars, the non-cyclic mono, di orpolysaccharides such as glucose, fructose, maltose, lactose or sucrose,cyclic or non-cyclic esters, cyclic or non-cyclic ethers, ketones,compounds combining several of these functions (ketones, carboxylicacids, ethers, esters, alcohols, amines, etc.), crown ethers,cyclodextrins and compounds containing at least sulphur, or phosphorusor nitrogen such as nitriloacetic acid, ethylenediaminetetraacetic acid,or diethylenetriamine, amino acids and zwitterrionic compounds, usedalone or in a mixture.

The impregnation and/or solubilization solvent is preferably water butany solvent known to a person skilled in the art can be used.

One or more other metallic elements can also be introduced into thecomposition of the catalyst used in the process according to theinvention. This metallic element can be selected from zinc, nickel,cobalt, tungsten, vanadium, niobium, tantalum, iron and copper. Thismetallic element is introduced at a content comprised between 0.01 and10%, and preferably between 0.02 and 5% expressed in % by weight ofmetal with respect to the weight of the mesoporous matrix based onoxide.

This metallic element can be provided by a compound selected from thesalts and/or oxides of zinc, nickel, cobalt, tungsten, vanadium,niobium, tantalum, iron and copper, preferably the salts and/or oxidesof zinc, nickel, cobalt, tungsten. Preferably, the compound is a salt, acarboxylate, an alkoxide or a cobalt, tungsten, vanadium oxide.

This compound can be introduced by impregnation onto the mesoporousmatrix before impregnation with at least one precursor according to theinvention of formula (I), by co-impregnation with said precursor(s)according to the invention or post-impregnation after impregnation withsaid precursor(s) according to the invention.

The deposition or the incorporation of at least one precursor accordingto the invention of formula (I), on the mesoporous matrix can also bedone directly during the synthesis of the mesoporous matrix based onoxide.

The synthesis methods used can be hydrolytic or non hydrolytic “sol-gel”methods by precipitation or by evaporation. The evaporation methods canrequire the use of a specific synthesis process such as spray-drying,the deposition of thin films, etc.

In the particular case of a hydrolytic sol-gel synthesis by spray-dryingleading to a catalyst having a mesostructured matrix based on oxidebeing obtained, the catalyst used in the process according to theinvention can be prepared according to the process comprising thefollowing stages:

a1) solubilization of the precursor comprising molybdenum and aluminium,of formula (I), and the precursors of the mesoporous matrix based onoxide of at least one element X in an aqueous or hydro-organic solutionin the presence of a pore-forming agent so as to form a colloidalsolution,

b1) spray-drying said colloidal solution so as to obtain spherical solidelemental particles incorporating the mesostructured matrix based onoxide and the precursor comprising molybdenum and aluminium of formula(I),

c1) optional stage of drying, calcination and/or steam treatment of thesolid particles obtained at the end of stage b1) at a pressure greaterthan or equal to 0.1 MPa or less than or equal to 0.1 MPa,

d1) stage of thermal activation of the dry solid particles at the end ofstage c1), at a pressure greater than or equal to 1 bar or less than orequal to 0.1 MPa, in a temperature range from 100 to 1000° C.

Preferably, the optional drying stage c1) is carried out in atemperature range from 20 to 200° C., preferably from 50° C. to 150° C.and preferably from 100° C. to 130° C. during a period of less than 72 hand preferably less than 24 h. Stage c1) can be carried out under anoxidizing, reducing or neutral atmosphere.

The stage of thermal activation d1) can be carried out under anoxidizing, reducing or neutral atmosphere.

Preferably, thermal activation stage d1) is carried out under a neutralatmosphere at atmospheric pressure in a temperature range from 200 to800° and preferably from 350 to 650° C. Preferably, the neutralatmosphere is nitrogen in a flow rate range from 0.01 to 10 NI/h pergram of solid obtained at the end of stage c1), preferably from 0.1 to 5NI/h per gram of solid obtained at the end of stage c1).

By hydro-organic solution is meant a solution of a mixture of water andan organic solvent. Preferably the hydro-organic solution is ahydro-ethanolic solution.

The metallic element(s) that can also be introduced into the compositionof the catalyst and preferably selected from cobalt, tungsten andvanadium can also be incorporated at any stage of this type of synthesisof the mesoporous matrix.

The pore-forming agent used in stage a1) is for example an ionic ornon-ionic surfactant compound or a mixture of the two.

The precursor(s) of the mesoporous matrix are precursors of the matrixbased on an oxide of at least one element X selected from silicon,aluminium, titanium, zirconium and mixtures thereof. Preferably, theprecursor(s) of the mesoporous matrix are precursors of the matrix basedon an oxide of at least one element X selected from silicon, titanium,zirconium and mixtures thereof. This/these precursor(s) can be anycompound comprising the element X and capable of releasing this elementin solution in reactive form. Thus, the precursor(s) of at least saidelement X of the matrix is(are) advantageously an inorganic salt of saidelement X of formula XZ_(n), (n=3 or 4), Z being a halogen, the NO₃ or aperchlorate group, preferably Z is chlorine. The precursor(s) of atleast said considered element X can also be one of the alkoxideprecursor(s) of formula X(OR)n where R=ethyl, isopropyl, n-butyl,s-butyl, t-butyl, etc. or a chelated precursor such as X(C₅H₈O₂)n, withn=3 or 4. The precursor(s) of at least said considered element X canalso be one (or more) oxide(s) or one (or more) hydroxides of saidelement X.

In the preferred case where X is silicon or a mixture of aluminium andsilicon, the silica and/or alumina precursors are precursors ofinorganic oxides well known to a person skilled in the art. The silicaprecursor is obtained from any source of silica and advantageously froma sodium silicate precursor of formula Na₂SiO₃, from a chlorinatedprecursor of formula SiCl₄, from an alkoxide precursor of formulaSi(OR)₄ where R═H, methyl, ethyl or from a chloroalkoxide precursor offormula Si(OR)_(4-a)Cl_(a) where R═H, methyl, ethyl, a being comprisedbetween 0 and 4. The silica precursor can also advantageously be analkoxide precursor of formula Si(OR)_(4-a)R′_(a) where R═H, methyl,ethyl and R′ is an alkyl chain or a functionalized alkyl chain, forexample by a thiol, amino, β-diketone, sulphonic acid group, a beingcomprised between 0 and 4. A preferred silica precursor istetraethylorthosilicate (TEOS). The alumina precursor is advantageouslyan inorganic salt of aluminium of formula AlZ₃, Z being a halogen or theNO₃ group. Preferably, Z is chlorine. The alumina precursor can also bean inorganic salt of aluminium of formula Al₂Z′₃, Z′ being the sulphategroup SO₄. The alumina precursor can be also an alkoxide precursor offormula Al(OR″)₃ or R″=ethyl, isopropyl, n-butyl, s-butyl or t-butyl ora chelated precursor such as aluminium acetylacetonate (Al(CH₇O₂)₃). Thealumina precursor can also be an aluminium oxide or hydroxide, forexample AlOONa.

In the case where the catalyst used in the process according to theinvention is obtained in the form of powder at the end of the differentprocesses of preparation disclosed above, the latter can be formedaccording to the methods well known to a person skilled in the art.Thus, it can be in the form of pelletized, crushed or sieved powder,granules, tablets, beads, wheels, spheres or extrudates (cylinders whichcan be hollow or not, multilobed cylinders with 2, 3, 4 or 5 lobes forexample, twisted cylinders), or rings, etc. Preferably, said catalyst isformed as extrudates.

During said forming operation, the catalyst used in the processaccording to the invention can optionally be mixed with at least oneporous oxide material acting as a binder so as to generate the physicalproperties of the catalyst suitable for the process according to theinvention (mechanical strength, attrition resistance etc.).

Said porous oxide material is preferentially a porous oxide materialselected from the group formed by alumina, silica, silica-alumina,magnesia, clays, titanium oxide, zirconium oxide, lanthanum oxide,cerium oxide, aluminium phosphates and a mixture of at least two of theoxides mentioned above. Said porous oxide material can also be selectedfrom alumina-boron oxide, alumina-titanium oxide, alumina-zirconia andtitanium-zirconium oxide mixtures. The aluminates, for examplemagnesium, calcium, barium, manganese, iron, cobalt, nickel, copper andzinc aluminates, as well as mixed aluminates for example thosecontaining at least two of the metals mentioned above, areadvantageously used as porous oxide material. Titanates can also beused, for example zinc, nickel, cobalt titanates. Mixtures of aluminaand silica and mixtures of alumina with other compounds such as forexample the group VIB elements, phosphorus, fluorine or boron can alsoadvantageously be used. It is also possible to use simple, synthetic ornatural clays of the dioctahedral phyllosilicate 2:1 type ortrioctahedral phyllosilicate 3:1 type such as kaolinite, antigorite,chrysotile, montmorillonite, beidellite, vermiculite, talc, hectorite,saponite, laponite. These clays can optionally be delaminated. Mixturesof alumina and clay and mixtures of silica-alumina and clay can also beadvantageously used. Various mixtures using at least two of thecompounds mentioned above are also suitable to act as binders.

Optionally, at least one organic adjuvant is also mixed during saidforming stage. The presence of said organic adjuvant facilitates formingby extrusion. Said organic adjuvant can advantageously be selected frompolyvinylpyrrolidones, cellulose polymers and derivatives thereof,preferably selected from cellulose ethers such as for example Methocel,marketed by the Dow Chemical company, polyvinyl alcohols, polyethyleneglycols, polyacrylamides, polysaccharides, natural polymers andderivatives thereof such as for example the alginates, polyesters,polyamides and aromatic polyamides, polyethers, poly(arylether)s,polyurethanes, polysulphones such as polysulphone ethers, heterocyclicpolymers, preferably selected from polyimides, polyimide ethers,polyimide esters, polyimide amides, and polybenzimidazoles.

The proportion of said organic adjuvant is advantageously comprisedbetween 0 and 20% by weight, preferably between 0 and 10% by weight andpreferably between 0 and 7% by weight, with respect to the total weightof the mesoporous matrix formed.

Metathesis Reaction

The process for the metathesis of olefins carried out by bringing theolefins into contact with the catalyst defined above, is advantageouslycarried out at a temperature comprised between 0 and 500° C., preferablycomprised between 0 and 400° C., more preferably between 20 and 350° C.and yet more preferably between 30 and 350° C.

The metathesis reaction of olefins can be carried out in gas phase or inliquid phase. The reaction can be carried out in batch mode, in astirred reactor, or in continuous mode, by passing the olefin reagentsthrough a fixed bed, a moving bed or a fluidized bed of catalyst.

The pressure at which the process according to the invention is carriedout is not critical. However, for an operation in liquid phase, it isadvantageous to maintain a pressure at least equal to the vapourpressure of the reaction mixture at the temperature of the reaction.

The reaction is preferably carried out in the absence of solvents.However, the reaction can be carried out in the presence of a solventsuch as a hydrocarbon, or a halogenated, aliphatic, cyclanic or aromatichydrocarbon.

Olefins capable of reacting by metathesis in the process according tothe invention can be linear olefins corresponding to general formulaR¹R²C═CR³R⁴, where R¹, R², R³ and R⁴, identical or different, arehydrogen or a hydrocarbyl radical with 1 to 20 carbon atoms, or olefinswith a cyclic structure, the ring comprising from 3 to 20 carbon atoms.

An olefin can either be reacted by itself, or several olefins can bereacted together in a mixture. The process according to the invention isin particular the cross-metathesis reaction of ethylene with 2-butene inorder to produce propylene, or the reverse reaction converting propyleneto a mixture of ethylene and 2-butene.

Other olefins capable of reacting by metathesis are the monoolefins orpolyolefins, linear or cyclic, bearing functional groups such as forexample halogen or ester groups. The process can also utilize, inco-metathesis a mixture of the above-mentioned olefins.

In the case of the production of propylene by metathesis betweenethylene and 2-butene, the 2-butene can preferably originate from adimerization reaction of ethylene in the presence of a homogeneous orheterogeneous catalyst known to a person skilled in the art. Forexample, the 2-butene can originate from a dimerization of ethylene inthe presence of a nickel complex of the NiCl₂(PBu₃)₂ type producing amixture of 1-butene and 2-butene by homogeneous catalysis. For example,the 2-butene can originate from a dimerization of ethylene in thepresence of a heterogeneous catalyst based on nickel of the NiSO₄/Al₂O₃type producing a mixture of 1-butene and 2-butene by heterogeneouscatalysis.

In the case of the production of propylene by metathesis betweenethylene and a mixture of 2-butene and 1-butene, a catalyst for theisomerization of 1-butene to 2-butene is preferably used in order tomaximize the propylene yield. For example, an oxide catalyst of the MgOor K₂O type can be used to isomerize the 1-butene to 2-butene.

Ethylene can advantageously be obtained by the dehydration of biosourcedethanol by any dehydration method known to a person skilled in the artin order to allow the production of biosourced propylene.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE represents productivity of the catalyst as a function oftime.

EXAMPLES

In the examples, the precursor of the phosphomolybdic acidheteropolyanion type PMo₁₂O₄₀ ³⁻.3H⁺ is commercially available and themolybdenum- and aluminium-containing precursor of the heteropolyanionsalt type ammonium aluminium molybdate [Al(OH)₆Mo₆O₁₈]³⁻.[(NH₄)⁺]₃.7H₂Ois prepared according to the method described in G. Wiese and J. Fuchs,Z. Naturforsch, 1967, 469, 73.

Example 1A (Not According to the Invention): Preparation of 6.7% Mo/SiO₂by Dry Impregnation with a Solution of PMo₁₂O₄₀ ³⁻.3H⁺.30H₂O

1.5 g of PMo₁₂O₄₀ ³⁻.3H⁺.30H₂O is dissolved at 60° C. in 7.3 ml ofdistilled water. On complete dissolution, a silica (S_(BET)=462 m²/g,V_(p)=0.75 ml/g) is impregnated with this solution. The solid obtainedis matured for 24 h at 25° C. under air. The resulting solid is dried inan oven at 120° C. for 24 h then activated under nitrogen at 550° C. for2 h.

Example 1B (According to the Invention): Preparation of 6.7% Mo+0.3%Al/SiO₂ by Dry Impregnation with a Solution of Al(OH)₆Mo₆O₁₈ ³⁻.(NH₄ ⁺)₃

2.3 g of [Al(OH)₆Mo₆O₁₈]³⁻.[(NH₄ ⁺)]₃.7H₂O is dissolved at 60° C. in 7.3ml of distilled water. On complete dissolution, a silica (S_(BET)=462m²/g, V_(p)=0.75 ml/g) is impregnated with this solution. The solidobtained is matured for 24 h at 25° C. under air. The resulting solid isdried in an oven at 120° C. for 24 h then activated under nitrogen at550° C. for 2 h.

Example 2: Metathesis of Propylene to Ethylene and 2-Butene

2 g of catalyst prepared in Example 1A and 1B is mixed in a proportionof 50% by weight with silicon carbide (SiC) in a double-jacketed fixedbed reactor. The heat transfer fluid of the double jacket is heated to70° C. Pure propylene is conveyed to the reactor by means of a Gilsonpump and the pressure is set at 4.5 MPa. The productivity of thecatalysts expressed in millimole of propylene consumed per gram ofcatalyst and per hour is quantified as a function of time denoted t (inhours denoted h) in the FIGURE.

The activity of the catalyst 1B according to the invention prepared byimpregnation with precursors comprising aluminium and molybdenum isgreater than the activity of catalyst 1A not according to the inventionand prepared by impregnation with a precursor based on molybdenum.

The stability of catalyst 1B according to the invention is better thanthe stability of catalyst 1A not according to the invention.

The invention claimed is:
 1. A process for the metathesis of olefinscarried out by bringing the olefins into contact with a catalystcomprising a mesoporous matrix and at least the elements molybdenum andaluminium, said elements being incorporated into said matrix using atleast one precursor comprising molybdenum and aluminium, in which thecatalyst is prepared by dry impregnation according to the processcomprising the following stages: a) solubilization of the precursorcomprising molybdenum and aluminium in a volume of solutioncorresponding to the pore volume of a preformed mesoporous matrix basedon oxide, b) impregnation of the preformed mesoporous matrix based onoxide with the solution obtained in stage a), optional maturation of thesolid thus obtained, c) optional stage of drying, calcination and/orsteam treatment of the solid obtained at the end of stage b), in atemperature range from 50° C. to 1000° C., and d) stage of thermalactivation of the solid obtained at the end of stage c), in atemperature range from 100° C. to 1000° C.
 2. The process according toclaim 1 in which the precursor is a precursor of a heteropolyanion salt,corresponding to formula (I):(Al_(a)Mo_(m)M_(b)X′_(x)O_(y)H_(h))^(q−)(C^(r+))_(c) .nH₂O  (I) inwhich, a is greater than 0, m is greater than or equal to 1, b isgreater than or equal to 0, x is greater than or equal to 0, y isgreater than or equal to 10, h is comprised between 0 and 12, q iscomprised between 1 and 20, r is comprised between 1 and 20, c iscomprised between 1 and 20, n is comprised between 0 and 200, x, m, y,h, n and q being integers, M being a metallic element selected fromzinc, nickel, cobalt, tungsten, vanadium, niobium, tantalum, iron andcopper, and X′ being phosphorus, silicon or boron, and C represents oneor more atoms, identical or different, hydrated or non-hydrated, fromthe elements of the periodic table capable of existing in cationic form.3. The process according to claim 2 in which the metallic element M iscobalt, tungsten, or vanadium.
 4. The process according to claim 2 inwhich the precursor of the heteropolyanion salt is an Andersonheteropolyanion salt of formula AlMo₆O₂₄H₆ ³⁻(C^(r+))_(c).nH₂O that canalso be written as the formula Al(OH)₆Mo₆O₁₈ ³⁻(C^(r+))_(c).nH₂O.
 5. Theprocess according to claim 4 in which the precursor of the Andersonheteropolyanion salt is[Al(OH)₆Mo₆O₁₈]³⁻[(C₆H₁₀N₃O₂)₂Na(H₂O)₂]³⁺6H₂O(C₆H₁₀N₃O₂=histidinium);[Al(OH)₆Mo₆O₁₈]³⁻ ₂{Na₂[Me₃N(CH₂)₂OH]₄}⁶⁺.8NH₂CONH₂. 4H₂O;[Al(OH)₆Mo₆O₁₈]³⁻.(H₃O⁺)[Cu(C₆NO₂H₄)(phenantroline)(H₂O)]⁺ ₂.5H₂O;[Al(OH)₆Mo₆O₁₈]³⁻[Al(H₂O)₆]³⁺.10H₂O, or [Al(OH)₆Mo₆O₁₈]³⁻[(NH₄)⁺]₃.7H₂O.6. The process according to claim 2 wherein C is hydrogen, an alkali, oralkaline-earth element, transition metal, a post-transition metal or arare earth, in hydrated or non-hydrated form, that is anoxygen-containing and/or nitrogen-containing and/orphosphorus-containing organic cation.
 7. The process according to claim6 wherein the cation is an ammonium or phosphonium cation.
 8. Theprocess according to claim 1 in which the mesoporous matrix is a matrixbased on the oxide of at least one element X that is silicon, titanium,zirconium, magnesium, lanthanum, cerium or mixtures thereof.
 9. Theprocess according to claim 1 in which the metathesis reaction is carriedout at a temperature comprised between 0 and 500° C.
 10. The processaccording to claim 9 in which the olefins are linear olefinscorresponding to formula R¹R²C═CR³R⁴, where R¹, R², R³ and R⁴, identicalor different, are hydrogen or a hydrocarbyl radical of 1 to 20 carbonatoms, or olefins with a cyclic structure, the ring comprising from 3 to20 carbon atoms.
 11. The process according to claim 1 in which themetathesis reaction is the cross-metathesis reaction of ethylene with2-butene, or the reverse reaction converting propylene to a mixture ofethylene and 2-butene.
 12. The process according to claim 1 wherein thepressure in (c) is ≥0.1 MPa.
 13. The process according to claim 1wherein the pressure in (c) is ≤0.1 MPa.
 14. The process according toclaim 1 wherein the pressure in (d) is ≥0.1 MPa.
 15. The processaccording to claim 1 wherein the pressure in (d) is ≤0.1 MPa.
 16. Aprocess for the metathesis of olefins carried out by bringing theolefins into contact with a catalyst comprising a mesoporous matrix andat least the elements molybdenum and aluminium, said elements beingincorporated into said matrix using at least one precursor comprisingmolybdenum and aluminium, in which the catalyst is prepared byimpregnation in excess according to the process comprising the followingstages: a′) solubilization of the precursor comprising molybdenum andaluminium in a volume of solution corresponding to between 1.5 and 20times the pore volume of the preformed mesoporous matrix based on oxide,b′) impregnation of the preformed mesoporous matrix based on oxide, withthe solution obtained in stage a′), filtration and recovery of thesolid, optional maturation of the solid thus obtained, c′) optionalstage of drying, calcination and/or steam treatment of the solidobtained at the end of stage b′) in a temperature range from 50° C. to1000° C., and d′) stage of thermal activation of the solid obtained atthe end of stage c′) in a temperature range from 100° C. to 1000° C. 17.The process according to claim 16 wherein the pressure in (c) is ≥0.1MPa.
 18. The process according to claim 16 wherein the pressure in (c)is ≤0.1 MPa.
 19. The process according to claim 16 wherein the pressurein (d) is ≥0.1 MPa.
 20. The process according to claim 16 wherein thepressure in (d) is ≤0.1 MPa.
 21. A process for the metathesis of olefinscarried out by bringing the olefins into contact with a catalystcomprising a mesoporous matrix and at least the elements molybdenum andaluminium, said elements being incorporated into said matrix using atleast one precursor comprising molybdenum and aluminium, in which thecatalyst is prepared according to the process comprising the followingstages: a1) solubilization of the precursor comprising molybdenum andaluminium and of the precursors of the mesoporous matrix based on oxideof at least one element X in an aqueous or hydro-organic solution in thepresence of a pore-forming agent so as to form a colloidal solution, b1)spray-drying said colloidal solution so as to obtain spherical solidelemental particles incorporating the mesostructured matrix based onoxide and the precursor comprising molybdenum and aluminium, c1)optional stage of drying, calcination and/or steam treatment of thesolid particles obtained at the end of stage b1) and d1) stage ofthermal activation of the dry solid particles at the end of stage c1),in a temperature range from 100 to 1000° C.
 22. The process according toclaim 21 wherein the pressure in (c) is ≤0.1 MPa.
 23. The processaccording to claim 21 wherein the pressure in (c) is ≥0.1 MPa.
 24. Theprocess according to claim 21 wherein the pressure in (d) is ≤0.1 MPa.25. The process according to claim 21 wherein the pressure in (d) is≥0.1 MPa.